This invention relates to session continuity for data packet wireless communication between networks using different communication standards.
Wireless communication proliferates with introductions of new transmission modes, communication protocols, and types of communication content. Examples of wireless communication systems include the public land mobile network (PLMN) and the wireless local area network (WLAN). In order for a mobile station, also referred to as user equipment (UE), to have access to a communication channel at various locations, increasingly a multi-access or multi-mode capability is incorporated into a single handheld UE. In addition, more functionality is being incorporated, including voice and data services. This integration poses challenges for seamless multi-access and session continuity as the UE moves within range of various access networks. The interworking between Third Generation Partnership Project (3GPP) (e.g., Global System for Mobile Communications/General Packet Radio Service (GSM/GPRS), Wideband Code Division Multiple Access (WCDMA), High Speed Downlink Packet Access (HSDPA)) and other access technologies such as IEEE 802.11 (WiFi), for instance, creates situations where interruptions in service or inability to multi-access are likely.
Multi-access refers to the ability to use multiple different access networks with a single communications device. The communications device may, for example, be connected to the Internet at first using a WLAN and, when outside the coverage of the WLAN network, using conventional circuit switch (CS) communications network.
Session continuity refers to maintaining upper level connections, for example transport level connection for a data packet protocol communication, when the access technology, that is the link layer, changes. This means, for example, that applications in a communications device or user of a communication device does not notice changes in access technology or interruptions in connectivity.
Examples of access technologies and communication services include traditional CS services (i.e., voice/Short Message Service (SMS)) along with some packet data service (e.g., presence and instant messaging) over GSM and Universal Mobile Telecommunication System (UMTS) access. Voice Over IP (VoIP), SMS-IP, and other packet data services (e.g., push-to-talk, video sharing, etc.) are available over Wireless Fidelity (WiFi) as well as UMTS/HSDPA. Some services, such as broadcast/multicast, are available over UMTS but not HSDPA/WiFi.
Considerable deployment of wireless infrastructure and UEs have been made utilizing IMS (IP Multimedia Subsystem), which is an internationally recognized standard that specifies interoperability and roaming between devices and provides bearer network control and security. It is also well integrated with existing voice and data networks, and hence makes IMS an important enabling technology for fixed-mobile devices. IMS also makes efficient use of existing circuit- and packet-switched technologies. The third generation (3G) IMS comprises a core network subsystem within the Universal Mobile Telecommunication System (UMTS), which uses the Session Initiation Protocol (SIP) to initiate, modify and terminate multimedia sessions. IMS also uses the IETF Session Description Protocol (SDP) to define session parameters, as well as negotiate codecs to be used during the multimedia session.
The IMS architecture requires that each UE register the network address provided by the access network by sending a unique device identifier that is authenticated by a home service provider. The problem thus is that a UE cannot maintain simultaneous registrations via different access technologies, such as WLAN, UMTS, 1x Evolution-Data Optimized (EV-DO), etc. Thus, it is not possible to maintain session continuity, to deliver services over a preferred access, or to have simultaneous services over different accesses.
With regard to the first scenario of maintaining session continuity over multiple access technologies, considerable development has addressed certain aspects of the problem. Mobile IP protocol takes care that data packets relating to a communication device's home IP address are routed from a home network to a care-of address at a mobile location of the communication device. While this allows certain simultaneous registration, the Mobile IP provisioning functionality at the network end imposes certain challenges for implementation. In addition, the Mobile IP protocol entails extra headers relating to tunneling to be present in data packets. Given the limited throughput typical of wireless access networks, this overhead tends to degrade the data transfer capabilities to utilize Mobile IP.
It has also been proposed that changes be made to the IMS architecture so that at the point where the communication converges from two access networks. The unique device identifier would be detected with the two different network addresses with some provisions made to allow simultaneous registrations when desired and to override a prior registration in other situations. However, such an implementation assumes that the two communication channels would have network addresses assigned by different proxy call session control function (P-CSCF), which is not necessarily the case.
With regard to the second scenario of automatically switching to a preferred access network, it is possible that a UE is within the coverage of multiple access networks (e.g., UMTS and WiFi). A user of the UE may prefer to receive a service (e.g., push-to-talk) over a particular access network (e.g., UMTS). However, this would require the UE to be registered in the IMS domain over both WiFi and UTMS access networks, which is prevented.
With regard to the third scenario of simultaneous services, it may be desirable for the UE to receive different services over multiple accesses simultaneously (e.g., video streaming over WiFi and push-to-talk over UMTS).